1. Dr. Alexandra I. Cristea http://www.dcs.warwick.ac.uk/~acristea/ XHTML

2. 2 What Is XHTML? XHTML stands for EXtensible HyperText Markup Language XHTML is almost identical to HTML 4.01 XHTML is a stricter and cleaner version of HTML XHTML is HTML defined as an XML application XHTML is a W3C Recommendation XHTML 1.0 became a W3C Recommendation January 26, 2000. All new browsers have support for XHTML.

3. 3 XHTML is a combination of HTML and XML (EXtensible Markup Language). XHTML consists of all the elements in HTML 4.01 combined with the syntax of XML.

4. 4 Why XHTML? We have reached a point where many pages on the WWW contain "bad" HTML. The following HTML code will work fine if you view it in a browser, even if it does not follow the HTML rules: This is bad HTML Bad HTML

5. 5 XML is a markup language where everything has to be marked up correctly, which results in "well-formed" documents. XML was designed to describe data and HTML was designed to display data. Today's market consists of different browser technologies, some browsers run Internet on computers, and some browsers run Internet on mobile phones or other small devices. The last-mentioned do not have the resources or power to interpret a "bad" markup language. Therefore - by combining HTML and XML, and their strengths, we got a markup language that is useful now and in the future - XHTML.

6. 6 How To Get Ready For XHTML XHTML is not very different from the HTML 4.01 standard. So, bringing your code up to the 4.01 standard is a good start. In addition, you should start NOW to write your HTML code in lowercase letters, and NEVER skip ending tags (like ).

7. 7 The Most Important Differences XHTML elements must be properly nested XHTML elements must always be closed XHTML elements must be in lowercase XHTML documents must have one root element

8. 8 XHTML Elements Must Be Properly Nested In HTML, some elements can be improperly nested within each other, like this: This text is bold and italic In XHTML, all elements must be properly nested within each other, like this: This text is bold and italic Note: A common mistake with nested lists, is to forget that the inside list must be within and tags.

9. 9 Wrong: Coffee Tea Black tea Green tea Milk

10. 10 Correct: Coffee Tea Black tea Green tea Milk

11. 11 XHTML Elements Must Always Be Closed Non-empty elements must have an end tag. This is wrong: This is a paragraph This is another paragraph This is correct: This is a paragraph This is another paragraph

12. 12 Empty Elements Must Also Be Closed This is wrong: A break: A horizontal rule: An image: This is correct: A break: A horizontal rule: An image:

13. 13 XHTML Elements Must Be In Lower Case This is wrong: This is a paragraph This is correct: This is a paragraph

14. 14 XHTML Documents Must Have One Root Element All XHTML elements must be nested within the root element. All other elements can have sub (children) elements. Sub elements must be in pairs and correctly nested within their parent element. The basic document structure is:...

15. 15 More XHTML Syntax Rules Attribute names must be in lower case Attribute values must be quoted Attribute minimization is forbidden The id attribute replaces the name attribute The XHTML DTD defines mandatory elements

16. 16 Attribute Names Must Be In Lower Case This is wrong: This is correct:

17. 17 Attribute Values Must Be Quoted This is wrong: This is correct:

18. 18 Attribute Minimization Is Forbidden This is wrong: This is correct:

19. 19 The id Attribute Replaces The name Attribute This is wrong: This is correct: Note: To interoperate with older browsers for a while, you should use both name and id, with identical attribute values, like this: IMPORTANT Compatibility Note: To make your XHTML compatible with today's browsers, you should add an extra space before the "/" symbol.

20. 20 The Lang Attribute The lang attribute applies to almost every XHTML element. It specifies the language of the content within an element. If you use the lang attribute in an element, you must add the xml:lang attribute, like this: Heia Norge!

21. 21 Mandatory XHTML Elements All XHTML documents must have a DOCTYPE declaration. The html, head and body elements must be present, and the title must be present inside the head element. This is a minimum XHTML document template: Title goes here Note: The DOCTYPE declaration is not a part of the XHTML document itself. It is not an XHTML element, and it should not have a closing tag.

22. 22 A simple (minimal) XHTML document simple document a simple paragraph

23. 23 Document Type Definitions (DTD) A DTD specifies the syntax of a web page in SGML DTDs are used by SGML applications, such as HTML, to specify rules for documents of a particular type, including a set of elements and entity declarations An XHTML DTD describes in precise, computer- readable language, the allowed syntax of XHTML markup There are three XHTML DTDs: STRICT TRANSITIONAL FRAMESET

24. 24 XHTML 1.0 Strict Use the strict DOCTYPE when you want really clean markup, free of presentational clutter. Use together with CSS.

25. 25 XHTML 1.0 Transitional Use the transitional DOCTYPE when you want to still use HTML's presentational features.

26. 26 XHTML 1.0 Frameset Use the frameset DOCTYPE when you want to use HTML Frames to split the web page into two or more frames.

27. 27 Validate your XHTML at: http://validator.w3.org/ http://validator.w3.org/ Tidy your code with tidy: http://cgi.w3.org/cgi-bin/tidy http://cgi.w3.org/cgi-bin/tidy

28. 28 XHTML Modularization For some purposes XHTML is too large and complex, and for other purposes it's too simple. By splitting XHTML into modules, the W3C (World Wide web Consortium) has created small and well-defined sets of XHTML elements that can be used separately for small devices, or combined with other XML standards in more complex applications. With modular XHTML, designers can: Choose the elements to be supported by a device Simplify XHTML for small devices Extend XHTML for complex applications by adding new XML functionality (like MathML, SVG, Voice and Multimedia) Define XHTML profiles like XHTML Basic (a subset of XHTML for mobile devices)

29. 29 Any Questions?